1 /* 2 * linux/arch/arm/mm/fault.c 3 * 4 * Copyright (C) 1995 Linus Torvalds 5 * Modifications for ARM processor (c) 1995-2004 Russell King 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License version 2 as 9 * published by the Free Software Foundation. 10 */ 11 #include <linux/module.h> 12 #include <linux/signal.h> 13 #include <linux/mm.h> 14 #include <linux/hardirq.h> 15 #include <linux/init.h> 16 #include <linux/kprobes.h> 17 #include <linux/uaccess.h> 18 #include <linux/page-flags.h> 19 #include <linux/sched.h> 20 #include <linux/highmem.h> 21 22 #include <asm/system.h> 23 #include <asm/pgtable.h> 24 #include <asm/tlbflush.h> 25 26 #include "fault.h" 27 28 /* 29 * Fault status register encodings. We steal bit 31 for our own purposes. 30 */ 31 #define FSR_LNX_PF (1 << 31) 32 #define FSR_WRITE (1 << 11) 33 #define FSR_FS4 (1 << 10) 34 #define FSR_FS3_0 (15) 35 36 static inline int fsr_fs(unsigned int fsr) 37 { 38 return (fsr & FSR_FS3_0) | (fsr & FSR_FS4) >> 6; 39 } 40 41 #ifdef CONFIG_MMU 42 43 #ifdef CONFIG_KPROBES 44 static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr) 45 { 46 int ret = 0; 47 48 if (!user_mode(regs)) { 49 /* kprobe_running() needs smp_processor_id() */ 50 preempt_disable(); 51 if (kprobe_running() && kprobe_fault_handler(regs, fsr)) 52 ret = 1; 53 preempt_enable(); 54 } 55 56 return ret; 57 } 58 #else 59 static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr) 60 { 61 return 0; 62 } 63 #endif 64 65 /* 66 * This is useful to dump out the page tables associated with 67 * 'addr' in mm 'mm'. 68 */ 69 void show_pte(struct mm_struct *mm, unsigned long addr) 70 { 71 pgd_t *pgd; 72 73 if (!mm) 74 mm = &init_mm; 75 76 printk(KERN_ALERT "pgd = %p\n", mm->pgd); 77 pgd = pgd_offset(mm, addr); 78 printk(KERN_ALERT "[%08lx] *pgd=%08lx", addr, pgd_val(*pgd)); 79 80 do { 81 pmd_t *pmd; 82 pte_t *pte; 83 84 if (pgd_none(*pgd)) 85 break; 86 87 if (pgd_bad(*pgd)) { 88 printk("(bad)"); 89 break; 90 } 91 92 pmd = pmd_offset(pgd, addr); 93 if (PTRS_PER_PMD != 1) 94 printk(", *pmd=%08lx", pmd_val(*pmd)); 95 96 if (pmd_none(*pmd)) 97 break; 98 99 if (pmd_bad(*pmd)) { 100 printk("(bad)"); 101 break; 102 } 103 104 /* We must not map this if we have highmem enabled */ 105 if (PageHighMem(pfn_to_page(pmd_val(*pmd) >> PAGE_SHIFT))) 106 break; 107 108 pte = pte_offset_map(pmd, addr); 109 printk(", *pte=%08lx", pte_val(*pte)); 110 printk(", *ppte=%08lx", pte_val(pte[-PTRS_PER_PTE])); 111 pte_unmap(pte); 112 } while(0); 113 114 printk("\n"); 115 } 116 #else /* CONFIG_MMU */ 117 void show_pte(struct mm_struct *mm, unsigned long addr) 118 { } 119 #endif /* CONFIG_MMU */ 120 121 /* 122 * Oops. The kernel tried to access some page that wasn't present. 123 */ 124 static void 125 __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr, 126 struct pt_regs *regs) 127 { 128 /* 129 * Are we prepared to handle this kernel fault? 130 */ 131 if (fixup_exception(regs)) 132 return; 133 134 /* 135 * No handler, we'll have to terminate things with extreme prejudice. 136 */ 137 bust_spinlocks(1); 138 printk(KERN_ALERT 139 "Unable to handle kernel %s at virtual address %08lx\n", 140 (addr < PAGE_SIZE) ? "NULL pointer dereference" : 141 "paging request", addr); 142 143 show_pte(mm, addr); 144 die("Oops", regs, fsr); 145 bust_spinlocks(0); 146 do_exit(SIGKILL); 147 } 148 149 /* 150 * Something tried to access memory that isn't in our memory map.. 151 * User mode accesses just cause a SIGSEGV 152 */ 153 static void 154 __do_user_fault(struct task_struct *tsk, unsigned long addr, 155 unsigned int fsr, unsigned int sig, int code, 156 struct pt_regs *regs) 157 { 158 struct siginfo si; 159 160 #ifdef CONFIG_DEBUG_USER 161 if (user_debug & UDBG_SEGV) { 162 printk(KERN_DEBUG "%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n", 163 tsk->comm, sig, addr, fsr); 164 show_pte(tsk->mm, addr); 165 show_regs(regs); 166 } 167 #endif 168 169 tsk->thread.address = addr; 170 tsk->thread.error_code = fsr; 171 tsk->thread.trap_no = 14; 172 si.si_signo = sig; 173 si.si_errno = 0; 174 si.si_code = code; 175 si.si_addr = (void __user *)addr; 176 force_sig_info(sig, &si, tsk); 177 } 178 179 void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs) 180 { 181 struct task_struct *tsk = current; 182 struct mm_struct *mm = tsk->active_mm; 183 184 /* 185 * If we are in kernel mode at this point, we 186 * have no context to handle this fault with. 187 */ 188 if (user_mode(regs)) 189 __do_user_fault(tsk, addr, fsr, SIGSEGV, SEGV_MAPERR, regs); 190 else 191 __do_kernel_fault(mm, addr, fsr, regs); 192 } 193 194 #ifdef CONFIG_MMU 195 #define VM_FAULT_BADMAP 0x010000 196 #define VM_FAULT_BADACCESS 0x020000 197 198 /* 199 * Check that the permissions on the VMA allow for the fault which occurred. 200 * If we encountered a write fault, we must have write permission, otherwise 201 * we allow any permission. 202 */ 203 static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma) 204 { 205 unsigned int mask = VM_READ | VM_WRITE | VM_EXEC; 206 207 if (fsr & FSR_WRITE) 208 mask = VM_WRITE; 209 if (fsr & FSR_LNX_PF) 210 mask = VM_EXEC; 211 212 return vma->vm_flags & mask ? false : true; 213 } 214 215 static int __kprobes 216 __do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr, 217 struct task_struct *tsk) 218 { 219 struct vm_area_struct *vma; 220 int fault; 221 222 vma = find_vma(mm, addr); 223 fault = VM_FAULT_BADMAP; 224 if (unlikely(!vma)) 225 goto out; 226 if (unlikely(vma->vm_start > addr)) 227 goto check_stack; 228 229 /* 230 * Ok, we have a good vm_area for this 231 * memory access, so we can handle it. 232 */ 233 good_area: 234 if (access_error(fsr, vma)) { 235 fault = VM_FAULT_BADACCESS; 236 goto out; 237 } 238 239 /* 240 * If for any reason at all we couldn't handle the fault, make 241 * sure we exit gracefully rather than endlessly redo the fault. 242 */ 243 fault = handle_mm_fault(mm, vma, addr & PAGE_MASK, (fsr & FSR_WRITE) ? FAULT_FLAG_WRITE : 0); 244 if (unlikely(fault & VM_FAULT_ERROR)) 245 return fault; 246 if (fault & VM_FAULT_MAJOR) 247 tsk->maj_flt++; 248 else 249 tsk->min_flt++; 250 return fault; 251 252 check_stack: 253 if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr)) 254 goto good_area; 255 out: 256 return fault; 257 } 258 259 static int __kprobes 260 do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs) 261 { 262 struct task_struct *tsk; 263 struct mm_struct *mm; 264 int fault, sig, code; 265 266 if (notify_page_fault(regs, fsr)) 267 return 0; 268 269 tsk = current; 270 mm = tsk->mm; 271 272 /* 273 * If we're in an interrupt or have no user 274 * context, we must not take the fault.. 275 */ 276 if (in_atomic() || !mm) 277 goto no_context; 278 279 /* 280 * As per x86, we may deadlock here. However, since the kernel only 281 * validly references user space from well defined areas of the code, 282 * we can bug out early if this is from code which shouldn't. 283 */ 284 if (!down_read_trylock(&mm->mmap_sem)) { 285 if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc)) 286 goto no_context; 287 down_read(&mm->mmap_sem); 288 } else { 289 /* 290 * The above down_read_trylock() might have succeeded in 291 * which case, we'll have missed the might_sleep() from 292 * down_read() 293 */ 294 might_sleep(); 295 } 296 297 fault = __do_page_fault(mm, addr, fsr, tsk); 298 up_read(&mm->mmap_sem); 299 300 /* 301 * Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR 302 */ 303 if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS)))) 304 return 0; 305 306 if (fault & VM_FAULT_OOM) { 307 /* 308 * We ran out of memory, call the OOM killer, and return to 309 * userspace (which will retry the fault, or kill us if we 310 * got oom-killed) 311 */ 312 pagefault_out_of_memory(); 313 return 0; 314 } 315 316 /* 317 * If we are in kernel mode at this point, we 318 * have no context to handle this fault with. 319 */ 320 if (!user_mode(regs)) 321 goto no_context; 322 323 if (fault & VM_FAULT_SIGBUS) { 324 /* 325 * We had some memory, but were unable to 326 * successfully fix up this page fault. 327 */ 328 sig = SIGBUS; 329 code = BUS_ADRERR; 330 } else { 331 /* 332 * Something tried to access memory that 333 * isn't in our memory map.. 334 */ 335 sig = SIGSEGV; 336 code = fault == VM_FAULT_BADACCESS ? 337 SEGV_ACCERR : SEGV_MAPERR; 338 } 339 340 __do_user_fault(tsk, addr, fsr, sig, code, regs); 341 return 0; 342 343 no_context: 344 __do_kernel_fault(mm, addr, fsr, regs); 345 return 0; 346 } 347 #else /* CONFIG_MMU */ 348 static int 349 do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs) 350 { 351 return 0; 352 } 353 #endif /* CONFIG_MMU */ 354 355 /* 356 * First Level Translation Fault Handler 357 * 358 * We enter here because the first level page table doesn't contain 359 * a valid entry for the address. 360 * 361 * If the address is in kernel space (>= TASK_SIZE), then we are 362 * probably faulting in the vmalloc() area. 363 * 364 * If the init_task's first level page tables contains the relevant 365 * entry, we copy the it to this task. If not, we send the process 366 * a signal, fixup the exception, or oops the kernel. 367 * 368 * NOTE! We MUST NOT take any locks for this case. We may be in an 369 * interrupt or a critical region, and should only copy the information 370 * from the master page table, nothing more. 371 */ 372 #ifdef CONFIG_MMU 373 static int __kprobes 374 do_translation_fault(unsigned long addr, unsigned int fsr, 375 struct pt_regs *regs) 376 { 377 unsigned int index; 378 pgd_t *pgd, *pgd_k; 379 pmd_t *pmd, *pmd_k; 380 381 if (addr < TASK_SIZE) 382 return do_page_fault(addr, fsr, regs); 383 384 index = pgd_index(addr); 385 386 /* 387 * FIXME: CP15 C1 is write only on ARMv3 architectures. 388 */ 389 pgd = cpu_get_pgd() + index; 390 pgd_k = init_mm.pgd + index; 391 392 if (pgd_none(*pgd_k)) 393 goto bad_area; 394 395 if (!pgd_present(*pgd)) 396 set_pgd(pgd, *pgd_k); 397 398 pmd_k = pmd_offset(pgd_k, addr); 399 pmd = pmd_offset(pgd, addr); 400 401 if (pmd_none(*pmd_k)) 402 goto bad_area; 403 404 copy_pmd(pmd, pmd_k); 405 return 0; 406 407 bad_area: 408 do_bad_area(addr, fsr, regs); 409 return 0; 410 } 411 #else /* CONFIG_MMU */ 412 static int 413 do_translation_fault(unsigned long addr, unsigned int fsr, 414 struct pt_regs *regs) 415 { 416 return 0; 417 } 418 #endif /* CONFIG_MMU */ 419 420 /* 421 * Some section permission faults need to be handled gracefully. 422 * They can happen due to a __{get,put}_user during an oops. 423 */ 424 static int 425 do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs) 426 { 427 do_bad_area(addr, fsr, regs); 428 return 0; 429 } 430 431 /* 432 * This abort handler always returns "fault". 433 */ 434 static int 435 do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs) 436 { 437 return 1; 438 } 439 440 static struct fsr_info { 441 int (*fn)(unsigned long addr, unsigned int fsr, struct pt_regs *regs); 442 int sig; 443 int code; 444 const char *name; 445 } fsr_info[] = { 446 /* 447 * The following are the standard ARMv3 and ARMv4 aborts. ARMv5 448 * defines these to be "precise" aborts. 449 */ 450 { do_bad, SIGSEGV, 0, "vector exception" }, 451 { do_bad, SIGILL, BUS_ADRALN, "alignment exception" }, 452 { do_bad, SIGKILL, 0, "terminal exception" }, 453 { do_bad, SIGILL, BUS_ADRALN, "alignment exception" }, 454 { do_bad, SIGBUS, 0, "external abort on linefetch" }, 455 { do_translation_fault, SIGSEGV, SEGV_MAPERR, "section translation fault" }, 456 { do_bad, SIGBUS, 0, "external abort on linefetch" }, 457 { do_page_fault, SIGSEGV, SEGV_MAPERR, "page translation fault" }, 458 { do_bad, SIGBUS, 0, "external abort on non-linefetch" }, 459 { do_bad, SIGSEGV, SEGV_ACCERR, "section domain fault" }, 460 { do_bad, SIGBUS, 0, "external abort on non-linefetch" }, 461 { do_bad, SIGSEGV, SEGV_ACCERR, "page domain fault" }, 462 { do_bad, SIGBUS, 0, "external abort on translation" }, 463 { do_sect_fault, SIGSEGV, SEGV_ACCERR, "section permission fault" }, 464 { do_bad, SIGBUS, 0, "external abort on translation" }, 465 { do_page_fault, SIGSEGV, SEGV_ACCERR, "page permission fault" }, 466 /* 467 * The following are "imprecise" aborts, which are signalled by bit 468 * 10 of the FSR, and may not be recoverable. These are only 469 * supported if the CPU abort handler supports bit 10. 470 */ 471 { do_bad, SIGBUS, 0, "unknown 16" }, 472 { do_bad, SIGBUS, 0, "unknown 17" }, 473 { do_bad, SIGBUS, 0, "unknown 18" }, 474 { do_bad, SIGBUS, 0, "unknown 19" }, 475 { do_bad, SIGBUS, 0, "lock abort" }, /* xscale */ 476 { do_bad, SIGBUS, 0, "unknown 21" }, 477 { do_bad, SIGBUS, BUS_OBJERR, "imprecise external abort" }, /* xscale */ 478 { do_bad, SIGBUS, 0, "unknown 23" }, 479 { do_bad, SIGBUS, 0, "dcache parity error" }, /* xscale */ 480 { do_bad, SIGBUS, 0, "unknown 25" }, 481 { do_bad, SIGBUS, 0, "unknown 26" }, 482 { do_bad, SIGBUS, 0, "unknown 27" }, 483 { do_bad, SIGBUS, 0, "unknown 28" }, 484 { do_bad, SIGBUS, 0, "unknown 29" }, 485 { do_bad, SIGBUS, 0, "unknown 30" }, 486 { do_bad, SIGBUS, 0, "unknown 31" } 487 }; 488 489 void __init 490 hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *), 491 int sig, const char *name) 492 { 493 if (nr >= 0 && nr < ARRAY_SIZE(fsr_info)) { 494 fsr_info[nr].fn = fn; 495 fsr_info[nr].sig = sig; 496 fsr_info[nr].name = name; 497 } 498 } 499 500 /* 501 * Dispatch a data abort to the relevant handler. 502 */ 503 asmlinkage void __exception 504 do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs) 505 { 506 const struct fsr_info *inf = fsr_info + fsr_fs(fsr); 507 struct siginfo info; 508 509 if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs)) 510 return; 511 512 printk(KERN_ALERT "Unhandled fault: %s (0x%03x) at 0x%08lx\n", 513 inf->name, fsr, addr); 514 515 info.si_signo = inf->sig; 516 info.si_errno = 0; 517 info.si_code = inf->code; 518 info.si_addr = (void __user *)addr; 519 arm_notify_die("", regs, &info, fsr, 0); 520 } 521 522 asmlinkage void __exception 523 do_PrefetchAbort(unsigned long addr, struct pt_regs *regs) 524 { 525 do_translation_fault(addr, FSR_LNX_PF, regs); 526 } 527 528